Algal blooms occur in many lakes, including Lake Erie, suspected source of the problem for Toledo and some residents in Southeast Michigan, where 500,000 people were told over the weekend not to drink, cook or clean dishes with their water after routine testing found cyanobacteria in treated water. The ban was lifted early today when testing showed the water was safe.

Toxic algae blooms, called “blue-green algae,” are a modern plague on freshwater and oceans, produced by the runoff of lawn and agricultural fertilizers, especially phosphorus and nitrogen, and also by pollution from livestock pens.

The runoff supercharges the water with nutrients, creating an unnatural amount of algae, capable of producing toxic cyanobacteria. The threat from this toxic bacteria borne by algae is worsening as climate change raises water temperatures, making lakes and ponds more susceptible to the phenomenon.

The continued use of chemical treatments for farmland and lawns also is spreading cyanobacteria blight, which recurs every summer in several hot spots around the US. Summer brings problems because bacteria thrive in warm water, but scientists have found recently that these dangerous bacteria can overwinter, below the ice, when there’s adequate sunlight.

Water treatment normally keeps people safe from drinking the potentially fatal cyanobacteria. The problem in Toledo is believed to have arisen by an abnormally large algae population in Lake Erie that produced a burst of the bacteria.

But while water treatment facilities keep drinking water free of cyanobacteria the vast majority of the time. This crisis in Toledo reminds us that these organisms also present a danger via direct contact. People and pets need to be aware that when algae grows rampantly in water, turning lakes green and leaving a telltale scum on top, it is not safe.

You should not wade, swim, boat in or even linger around it. People have become ill just from boating or jet-skiing in affected waters, according to the US Centers for Disease Control.

And while we might intuitively keep our children and ourselves out of obviously polluted waters, many people have found out the hard way that their pets are particularly endangered.

Dogs at Risk

Dogs that take to the water can be sickened, and many have died. This Labrador dog, who played fetch in an infected Minnesota lake this summer, became seriously ill within hours of apparently ingesting the toxin.

Pets are especially at risk because they’ll not hesitate to go into affected waters, and may drink from the lake or pond and ingest further algae by licking it off their fur. Their smaller body mass also makes them vulnerable, according to the Ohio Department of Health.

Not all algae is harmful, obviously. But the blue-green algae blooms induced by chemical pollution can be deadly when they contain cyanotoxins. Pets that fall ill from this class of bacteria exhibit symptoms similar to those that affect humans, vomiting, diarrhea, lethargy, weakness, disorientation, respiratory difficulties. Here, according to the CDC, ODH and other government sources, is what to watch for:

Watch out for these signs of trouble

Some blooms can look like foam, scum, or mats on the surface of fresh water lakes and ponds.

The blooms can be blue, bright green, brown, red or purplish, and may look like paint floating on the water. Some blooms may not affect the appearance of the water.

Even though “blue-green algae” is the typical medium in which cyanobacteria grow, it’s not possible to tell by looking whether a bloom contains the cyanobacteria. Tests are required. Even water recently cleared of the telltale algae may still contain toxic cyanobacteria.

An infected lake may have a bad odor. The problem with this is that unaffected lakes also might not have such a keen smell.

What you can do

If your pet is exposed to blue -green algae, you should rinse the animal off immediately.

Call your veterinarian, ASAP. There is no antidote for this cyanobacteria-induced illness. But, depending on the exposure, a veterinarian may be able to intervene. In some types of cyanobacterial infections, oxygen may provide support to enable recovery.

In the case of human exposure, head to the nearest Emergency Room. Powdered charcoal is one possible treatment for absorbing the toxins, according to the CDC.

Check with your state health or parks department about lakes where you recreate. Many states keep a list of lakes known to be affected by a toxic algal bloom.

Report any musty smelling water to local authorities.

If you want to be part of the larger solution, quit using synthetic fertilizers on your lawn, and go with organic. Organic fertilizers are not as soluble as the inorganic synthetics that wash off into sewers or directly into waterways.

If you live on a lake, the New York Department of Environmental Conservation recommends that you reduce the use of phosphorus and nitrogen washing off into the lake by “limiting lawn fertilization, maintaining septic tanks and shoreline buffers, reducing erosion and stormwater runoff, and maintaining water movement.”

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